The present invention relates to a technology for enabling mutual communications by connecting a local area network (LAN) with a storage area network (SAN) which cannot communicate directly with each other since they have different network protocols. The present invention enables a direct connection between the LAN and the SAN, in other words, an access to a storage device (a magnetic disk or an optical disk) connected to the SAN or a server from a personal computer (PC) or a work station (WS) which is connected to the LAN.
With explosive widening of the Internet, the transmission control Protocol (TCP) and the Internet protocol (IP) emerged as standard protocols for communications via a network. The TCP and IP are typical protocols for the LAN constructed in a company or a school. As a physical network used for the LAN, Ethernet is the mainstream. There are 10 Mbps (mage (a million) bit per second), 100 Mbps, and 1 Gbps (giga (a billion) bit per second) of Ethernet lines having different transmission speeds. It should be noted that, however, they are different only in the transmission speed. These Ethernet lines use the same packet format on a physical network, thus securing mutual connectivity.
The widely spread LAN is suitable for a connection between information processing units such as a PC and a WS, but they are unsuitable for connecting information storage devices such as a magnetic disk and an optical disk. It is because, while data communicated between the information processing units has a relatively small amount such as several hundreds of bytes or so (for example, a processing request and a processing result), data sent or received between information storage devices has a very large amount such as several kilobytes to several megabytes (for example, customer information). The SAN was invented as a network suitable for communications with these information storage devices. The SAN expanded the conventional small computer serial interface (SCSI) connection. As a physical network used for the SAN, Fibre Channel is the mainstream. The Fibre Channel has the following features appropriate for a connection with information storage devices:    (1) Enabling a 1-Gbps or higher speed communication;    (2) Enabling a long-distance communication of several to tens of kilometers; and    (3) Enabling a very reliable communication since it has a flow control mechanism and a resending control mechanism.The SAN is continuously spreading around large-sized data centers. Therefore, it is expected that future networks in companies or schools will be composed of LANs and SANs.
To connect the LAN with the SAN directly, some methods are suggested. Internet Engineering Task Force (IETF) is going on with standardizing the following technologies, some of which completed to be standardized:
(1) RFC2625: IP and ARP Over Fibre Channel
(2) DRAFT: Fibre Channel Over TCP/IP
These technologies secure connectivity between the LAN and the SAN communicating with each other over IP by encapsulating IP for a Fibre Channel packet.
On the other hand, National Committee for Information Technology Standards (NCITS) is going on with standardizing the following technologies for directly connecting a wide area network (WAN) with the SAN:
(3) Fibre Channel Back Bone Rev 4.7
On a parallel with the standardization of these technologies, there are venture companies performing anticipatory product development and prior investment in the markets mainly in the U.S. Under the existing conditions, however, the mutual connectivity has not been secured yet between the LAN and the SAN.